New genetic technologies, combined with a well-characterized genome, make the mouse the preferred mammalian model for human disease. The generation and characterization of mouse strains harboring genetically predetermined pathobiological syndromes is critical to biomedical research and researchers at the Jackson Laboratory (TJL) are at the forefront of this endeavor. Full exploitation of mouse models relies on access to critical technologies. Over 30 percent of TJL's research staff rely heavily on cell sorting to carry out funded studies in stem cell biology, inflammation, immunology, diabetes, chromosome manipulation and cancer research. It is essential for the funded Staff to enrich specific cell populations with: unique cell surface antigens, differences in cell cycle status, fluorescing transgenes, secretory proteins, aneuploidy, etc. A 13 year old venerable but outmoded Becton-Dickinson (B-D) FACStar is no longer reliable nor can it be upgraded to take on more complicated tasks. The basic B-D FACSVantage SE sorting flow cytometer is more sophisticated than the FACStar and has optional features that cover the needs of PIs at TJL. High speed sorting through a Circulating Refrigerated Unit reduces cell loss; AccuDrop provides less interference from surrounding drops during collection; SortWatch continuously monitors the sort and allows corrections before a crisis; FACSDiVa gives high resolution multi-parameter sorts; a third (He/Ne) laser is essential for multi-parameter analyses; additional Detectors eliminate false positives such as dead cells; TurboSort Plus rapidly sorts rare populations; CloneCyt Plus programs cell release into individual receptacles; Pulse processor Plus detects cells in cycle; and a FACStation analyzes data and frees the FACSVantage for its defined purpose. Funds are requested to purchase the FACSVantage SE and the optional equipment for TJL's Flow Cytometry Service. This will provide a cost-effective way to fill an urgent need of TJL's principal investigators.